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|
datatype list t = Nil | Cons of t * list t
fun length (t ::: Type) (ls : list t) =
let
fun length' (ls : list t) (acc : int) =
case ls of
Nil => acc
| Cons (_, ls') => length' ls' (acc + 1)
in
length' ls 0
end
fun rev (t ::: Type) (ls : list t) =
let
fun rev' (ls : list t) (acc : list t) =
case ls of
Nil => acc
| Cons (x, ls') => rev' ls' (Cons (x, acc))
in
rev' ls Nil
end
|
